Perry the platypus

Perry the Platypus, code named Agent P, or simply Perry, is Phineas and Ferb's pet platypus, who, unbeknownst to his owners, lives a double life as a secret agent for the O.W.C.A. (The Organization Without a Cool Acronym a.k.a. "The Agency"), a secret spy organization that employs animal spies. In the Agency, his immediate superior is Major Monogram While undercover, Perry can normally be found with his owners, Phineas and Ferb. As their pet, he lives up to the expectations for a platypus and "doesn't do much". Even though Candace would describe him as just a mindless, smelly animal, Perry still shows signs of intelligence when he's pretending to be a normal pet. He is also serious while on duty as an agent, even in front of Major Monogram when he does anything silly or makes fun of something and he is now human sized or giant or big or tall